Attempts to simulate actual firing conditions in the training of military personnel is well known. There have been various approaches taken in the prior art to achieve variable muzzle velocity for practice mortar shell. The U.S. Pat. No. 3,946,637 and patents cited therein are directed to various types of mortar configurations for adjusting the velocity of a single charge cartridge. This involves a modification of the standard mortar tube of the firearm from which the projectile is fired.
The U.S. Pat. No. 2,801,586 discloses a subcaliber mortar training shell which was developed to simulate the firing of a regulation sized mortar in training the combat men. This prior art device involves a fairly complex structural configuration for the mortar shell with charges being implanted in the shell body portion of the projectile. There is a manipulation requiring alignment of apertures and a modification which must be done to the fire arm barrel in order to use the subcaliber mortar trainer shell of the prior art. Since the firearm and the shell of this earlier U.S. Pat. No. 2,801,586 require significant modification with respect to the actual regulation sized firearm and projectile, the simulation of actual firing conditions is not possible.